Small and fractional horse-power dynamoelectric machine construction



March 30, 1965 P. w. THOMPSON ETAL 3, 7

SMALL AND FRACTIONAL HORSE-PQWER DYNAMOELECTRIC MACHINE CONSTRUCTION Filed Nov. 4, 1958 2 Sheets-Sheet 1 a .la u

\\\\ n Z r 5 a W W; w New? fig pwwd a m v 4 W 0.. w a a, %v t/V/ March 30, 1965 P. w. THOMPSON ETAL 3,176,172

SMALL AND FRACTIONAL HORSE-POWER DYNAMOELECTRIC MACHINE CONSTRUCTION Filed Nov. 4, 1958 2 Sheets-Sheet 2 pgs.

fin e/Ytons. Page 11/. Mam 0.9a, Lawrence 144 M' ii; a

{y flzi'tor-ne United States Patent This invention relates to dynamoelectric machines, and more particularly to small and fractional horsepower machines.

As is well known in the electric motor and generator field, each dynamoelectric machine generally includes a stationary member, commonly referred to as a stator, concentrically arranged relative to a rotatable member called a rotor, with the rotor being separated from the stator by an annular air gap. The operation of such machines is achieved by the establishment of a magnetic flux held across the air gap between the stator and rotor members. The strength and effectiveness of this field is controlled to a great extent by the dimensions of the air gap; that is, as the radial width of the air gap is decreased, less magnetic material and exciting coils are required to produce a given field strength and machine performance. Therefore, it is very desirable to maintain the radial width of the air gap at a small value without any interference between the rotor and stator members during their relative rotation. Furthermore, it is also important that the air gap be of a controlled and uniform width throughout its circumference, for among other reasons, an olfcenter rotor during machine operation will causeunduly high vibrations, excessive noise, and a marked decrease in machine performance. Moreover, misalignment between the rotor shaft and the bearings carrying the rotor assembly will similarly affect the proper operation of the machine, and will cause premature bearing failures.

In addition to the rotor being centered radially in the air gap, it should also be centered axially and its shaft should not move appreciably in the axial direction .dur-. ing rotation. Any excessive amount of axial movement, known as an end play, will detrimentally affect machine operation.

Heretofore, in order to obtain a motor or generator, suitable for mass production purposes, which hadthe requisite bearing and shaft alignment, accurate rotor and stator concentricity, and proper rotor shaft end play, the manufacturing practices by necessity have been costly, and in many instances have resulted in a machine of relatively complex construction. For example, one method of manufacture necessitated the holding of a large number of dimensions within very close limits. Close tolerances between machine parts were required because of the manner in which the rotor, stator, and rotor bearings were located with respect to each other. For instance, if the stator were bolted to the motor frame, it would be necessary to locate accurately corresponding holesin the stator core and the motor frame with respect to hearing mounts so that the radially inner surface of the stator core would be coaxial with the axis of the bearing and rotor. Thus, the control of the air gap between the stator and the rotor was limited by the dimensional tolerances required for the component parts, from the rotor shaft, radially out to the inside of the housing. These tolerances, being cumulative, placed a practical limitation on the minimum radial width of the air gap, since the air gap width must be sufficient to allow for the dimensional variations of rotors and stators and other component parts of the motor within such manufacturing allowances.

Certain other methods of assembly and the resultan motor constructions were designed to obviate the need for the above-mentioned close tolerances required on the end shields, frames, stator outer diameter, bearing and rotor shaft assembly, etc., but were not entirely satisfactory for one reason or another. For example, one such method provides a meanswhich simulates the rotor and shaft assembly of the electric machine, with the outside diameter of the simulated or dummy rotor portion being larger than the actual rotor by the amount of the air gap. This dummy rotor is initially placed into the rotor bearing means, which are fixedly secured to the frame, in a position simulating the finally assembled position of the rotor and shaft assembly. The wound stator core is thereafter assembled over the dummy rotor and welds are then made between the frame, which fixedly carries the bearings, and the outer periphery of the stator core by any suitable means. After the welding step has been completed, the dummy rotor is withdrawn, leaving the stator secured in place with provision for a controlled annular air. gap. The rotor assembly is thereafter inserted into the stator and frame unit. This method, of course, is suitable only for use with unit bearing machines, that is, machines in which the rotor is supported at one end only and, thus is not available for use with the great majority of machines wherein the rotor is supported at both ends. Furthcr, since in this method, the stator core and frame are secured by a weld, stresses are introduced which have an adverse etfect, as will be explained hereinafter, particularly in destroying at least to some extent,- the bearing alignment obtained before the weld is made.

Yet other manufacturing procedures employing the dummy rotor technique have been proposed for assem-. bling machines in which the rotor is supported at both ends. But in these procedures it is necessary to provide detachable end shield assemblies in order that the dummy rotor can be removed after securement of the various parts and the rotor assembly substituted therefore. In some instances, type-metal casting or the like is used to mechanically secure the various parts together. The machine construction and method of assembly as disclosed in the Soames Patent No. 598,540 is typical of this approach. Generally speaking, initially the dummy rotor and shaft assembly is arranged within the stator core member. This unit is then positioned within a frame with the outer surface of the stator core memberbeing spaced from the frame. Normally, the frame is formed with a flange against which one side of the stator core member is held; a ring or other means is placed against the other side of the stator member and the member is held therea recess within which a shaft bearing is loosely carried,

, cesses and bearings.

are bolted to the frame after the bearings have been placed onto the shaft. The assembly is then turned on end and molten type-metal is poured into the spaces and grooves between the frame and stator, and between the boss re- The metal is then allowed to set. Thus it can be seen that the metal fills the spaces and. grooves and mechanically links. the adjacent parts together. The provision of grooves or other means into which the material may be run, is essential for this me chanical interlock of parts, since type-metal or the like does not have adhesive or bonding characteristics to fix-Q edly hold the adjacent parts in the desired relationship. Thereafter, one end shield assembly is removed and the dummy rotor assembly is replaced by the machine rotor. The end shield is once again bolted to the end of the frame, completing the assembly.

The disadvantages of this procedure and resultant machine construction are manifold. This assembly procedure is adaptable for use only with a detachable end shield type of machine wherein'a portion of the machine may be disassembled in order to remove the dummy rotor. Further, the fact that the machine must be partially disassembled and the dummy rotor and shaft assembly replaced by a unit which may have dilferent tolerances, the prior alignment of the parts very often is destroyed and the shaft. end play is changed. Tightening of the bolts also has a tendency to change the alignment obtained prior to the removal of the dummy rotor. Moreover, the use of type-metal to interlock the parts has not proven to be too satisfactory. For example, the machine structure is more complex than is desired, for the frame must have means to hold the stator therein; e.g., flanges. Also, grooves,-and the like must be provided for retaining the metal for mechanical locking purposes. In addition, due to the difficulty experienced in the application of the molten material and the tendency of the material to shrink once it solidifies, a relatively large space must be provided to hold the metal and an excessive amount of metal must be used., Then, too, like welding, due to the fact that metal has a tendency to shrink, stresses are introduced adversely affecting alignment of the parts. Further, not only is the above assembly procedure overly complicated, but also with the use of metal, the par-ts must be in a relative final position before the molten metal can be applied, a limiting factor in the assembly set up.

As is readily apparent, previous assembly procedures have been costly, both from the standpoint of number and accuracy of operations employed in the mass production manufacture of the motor. Equally important, none of the foregoing methods insured that the motors produced by the mass production processes were continually of a high standard; i.e., each motor provided with a maxirnum degree of rotor and stator concentricity and proper bearing and shaft alignment. Bolting, clamping, welding, metal mechanical locking or the like of the rotor supporting assembly to the stator frequently created or added undesirable stresses which tended to deform both the statorrotor concentricity and the bearing alignment after completion of the assembly of the motor. With such stresses present, a readjustment and realignment of the parts takes place, destroying the degree of concentricity and alignment achieved during the prior assembly steps. In some instances, the proper amount of rotor shaft end play was difiicult to set. Furthermore, the kind of securing means and the associated motor assembly practices were generally limited in use with one specific type of motor; e.g. unit bearing type.

Accordingly, it is a primary object of the present invention to provide an improved low-cost dynamoelectric machine which is of novel construction permitting substantial simplification of the method of manufacture, and which includes excellent accuracy of bearing alignment and rotor and stator concentricity.

A further object is the provision of a machine in which the number of parts are kept at a minimum, and in whose production the assembly operations are substantially Ieduced.

Further objects and advantages will become apparent as the following description proceeds and the subject matter which we regard as our invention is pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the objects of this invention in one form thereof, we provide an improved dynamoelectric machine in whichthe rotor supporting means, including the at least one end frame fixedly mounting a shaft supporting bearing is attached to the stationary member by means of a hardened structural adhesive bonding material. More specifically, the end frame assembly is positioned adjacent one of the end surfaces of the stationary member and has portions projecting into holes formed in one of the end surfaces at locations radially spaced between the inner and outer surfaces of the stationary member, the hardened bonding material is disposed within theholes accommodating the end frame portions and rigidl secures the end I 4- frame and stationary member together in fixed relation for the operating life of the machine if such is desired.

For a better and more complete understanding of the invention, reference should be had to the following description taken in conjunction with the accompanying drawings which illustrate embodiments of the present invention.

In the drawings:

FIG. 1 is a perspective view of an electric motor embodying our invention in one form thereof;

FIG. 2 is a partial side view in cross section of an assembly fixture with a motor end shield assembly in position thereon, illustrating one step of the improved method of this invention;

FIG. 3 is a similar view to FIG. 2 showing the next assembly step in the preferred method of the invention, with the rotor assembly placed in the fixture and end shield assembly; 7

FIG. 4 is a similar view to FIG. 3 illustrating a subsequent step in the method, with the addition of the stator assembly, the shim means between the stator and rotor members and the adhesive bonding material;

FIG. 5 shows the curing step for hardening the bonding material in the assembled electric motors;

FIG. 6 is an axial view, partially in cross-section, of the completed electric motor shown in FIG. 1 after the curing step but prior to removal from the assembly fixture, to illustrate in more detail the assembled electric motor and assembly fixture;

FIG. 7'is a plan view, broken away in part, of the end shield assembly in position on the fixture as shown in FIG. 2, to illustrate more clearly the assembly fixture;

FIG. 8 is an axial view, partially in cross-section, of a motor embodying our invention in a second form thereof;

FIG. 9 is an axial view, partially in cross-section, of a totally enclosed stator encapsulated motor embodying our invention in another form thereof;

FIG. 10 is an axial view, partially in cross-section, of a detachable end shield motor embodying our invention in yet another form; and

FIG. 11 is an axial cross-sectional view of a unit bearing motor embodying our invention in still another form.

Referring now to the drawings in more detail, FIGS. 1 and 6 illustrate the invention as applied to a small motor of the squirrel-cage induction type. The motor identified generally by numeral 20 in FIG. 1 comprises a stator core member 21 and rotor member 22 which are secured together for relative rotation by supporting means generally indicated at 23. The stator member 21 comprises a magnetic core formed of a plurality of stacked thin laminations 24 of magneticmaterial fixedly secured together with the usual field coils 25 wound thereon. The stator core 21 is provided with an accurately dimensioned inner surface or bore 26 which is finished to a cylindrical form of predetermined diameter. The rotor 22, which is concentrically secured to a shaft 27 in any suitable fashion (not shown), is arranged coaxially and concentrically within stator bore 26 so as to define an annular air gap 28 therebetween. The rotor has the standard squirrel cage type winding which includes a plurality of equispaced conductors 29 extending the axial length of the rotor, and a pair of end rings 39 and 31 at the respective ends of the rotor, which join all the conductors 29 together electrically.

The supporting means 23 in its preferred form comprises two identical end shield assemblies 32 and 33. As is better shown in FIG. 2, each end shield assembly in cludes a substantially U-shaped stamped metal member 34 having a pair of diametrically disposed leg portions 35 joined by a bight or connecting section 36. The leg portions 35 are so bent that the space between their outer ends is slightly greater than the width of the stator core member 21. Centrally of each section 36 and extending axially therethrough, is a bearing 37, adapted to receive the rotor shaft 27 (shown in FIG. 3). Bearing 37, which may be of the sintered variety, is fixedly secured to section 36 by any suitable means, such as, for example, by a groove and fiange arrangement indicated at 38. A hearing and shaft lubricating means in the form of a cylindrical oil-impregnated felt body 39 may be provided in juxtaposed relation with the bearing 37. In addition, each end shield assembly contains mounting means in the form of a hub and resilient annulus generally shown at 40, which may be used for mounting the motor onto a stationary motor supporting base member (not shown). A pair of apertures 41 are provided in section 36 for purposes which will become apparent as the description proceeds.

Now, in accordance with the improved method of the present invention, which is now disclosed and claimed in our co-pending divisional applicational Serial No. 79,665 filed December 30, 1960, the motor 20 is assembled by initially placing one end shield assembly 32 onto an assembly fixture 42 with the leg portions of the end shield extending upwardly, as shown in FIGS. 2 and 7. For purposes of illustration only, assembly fixture 42 is shown in FIG. 6 as comprising a cast base plate 43 having a pair of upwardly extending side walls 44 and an integrally formed, centrally positioned, raised block portion 45. The block portion 45 is provided with a longitudinally extending bore 46 in which is pivotally mounted, by suitable means such as pin 47, ,a bar 48. At each end of the bar, there is pivotably attached an arm 49 which is adapted to fit through apertures 41 of each end shield member 34. An upper plate 50 is fixedly attached, such as by welding (not shown) to the upper ends of the side walls 44. Plate 50 is formed with a pair of spaced apart apertures 51 through which arms 47 movably extend. Integrally formed and centrally disposed on the upper surface of plate 50 is an annular stud portion 52, adapted to butt against outer end surface 53 of bearing 37 and support the end shield assembly 32. A shaft-receiving recess 54 is provided in the stud portion 52 and plate 50 with a screw means 55 communicating with and in adjustable relationship to the lower portion 56 of recess 54.

The significance of the afore-described fixture construction will become more apparent as the description proceeds.

As shown in FIG. 3, after the end shield assembly 32 is positioned on the assembly fixture 42 with arms 49 extending upwardly through end shield apertures 41 and with stud portion 52 supporting the end shield assembly, the rotor and shaft assembly 57, which has a thrust washer 58 and 59 respectively mounted at each end of the rotor 22, is arranged in the fixture assembly in a vertical manner, so that the lower washer 58 lies between end ring 30 and the inner end face 60 of bearing 37. A portion of shaft 27 extends through bearing 37 and into recess 54 of the fixture. Thus, it can be seen that screw means 55 can be adjusted to contact shaft end 61, raising the rotor and shaft assembly a predetermined distance away from the inner end face 60 of bearing 37, which rests on stud 52, thereby setting a selected amount of shaft end play into the motor as will be more completely explained hereinafter.

, In order for rotor 22 to be propertly assembled within stator 21, suitable means are provided for maintaining the air gap as desired. In the preferred method, as illustrated in FIG. 4, the means comprises shim means 62, composed of a meltable material (the composition to be further discussed below). When this type of shim means is used, it may be provided as disclosed and claimed in the copending application of Lawrance W. Wightman, Serial No. 757,652, now abandoned, filed August 26, 1958 and assigned to the same assignee of the present invention. However, it will be obvious to those skilled in the art that the method of this invention encompasses the use of any removable shim means, which serve to control the positioning of the rotor within the stator member. For example, metal gage strips of predeter mined thickness could be used; however, means, such as suitably placed apertures, must be included in the motor shell for removal of the metal shim means after the assembly of the parts has been completed. These apertures may be closed by any suitable means after the metal shim means have been removed, if it is desired to use metal shim means in assembling totally enclosed motors. Moreover, it should be apparent that the precise method and time of fixing the shim means in the assembly is dependent upon the type; i.e., meltable or metal, and the form used. Therefore, for purposes of illustration only, the meltable shim means shown are applied to the bore or inner surface 26 of the stator core 21 prior to assembly of the stator 21 with the rotor 22.

The stator 21 with shim means 62 is lowered over the motor assembly 22 until end face 63 of the stator laminations rests on the ends of fixture arms 49. The shim means 62 accurately and concentrically positions and maintains the stator and rotor members relative to each other. The length of the arms 49 is such that the lower end face 63 of the stator core 21 fits below the upper part of the end shield leg portion 35 adjacent and preferably spaced from the outer surface 64 of stator core member 21. In other words, the length of arms 49 determines the amount of overlap or iuterfit between the respective parts. Since the arms 49 are pivotally mounted and support the stator at spaced apart points along an axis perpendicular to the transverse axis of the stator core 21, dimensional variations between each stator core are absorbed by the assembly fixture. It will also be observed that the assembly fixture permits the stator 21 and rotor 22 which are being maintained in a positive relationship with regard to each other by shim means 62, to float freely relative to the end shield assembly 32. After the stator is in place on the arms 49, structural bonding means 65, more fully described hereinafter, in the form of an adhesive material in a plastic state, is applied, by any suitable means such as by squirting (not shown) to the space 66 between the stator outer surface 64 and the adjacent parts 67 of the end shield leg portion 35 in a sufiicient amount to substantially fill the space.

Thereafter, the other end shield assembly 33 is mounted over the upper end of the rotor and stator assembly with the inner end surface of the upper bearing 34 resting against thrust washer 59, which is carried by end ring 31. Structural bonding means is applied, like before, to the space between the outer surface 64 of the stator and the adjacent parts 68 of the end shield leg portions 35. Of course, it will be obvious to those skilled in the art that the structural adhesive material could equally as well be applied to a portion of the outer periphery of the stator core 21 or to a portion of the inner surface of the end shield leg portions 35, or to both portions, before assembly of the parts as well as after, without departing from the true scope and spirit of the invention.

At this point in the assembly procedure, it should be observed that the motor parts are in a final assembled form. The shim means 62 maintain the rotor and stator members in a definite and concentric relation, while the plastic bonding means 65 allows the two end shield as semblies 32 and 33, which in this embodiment form the rotor supporting means, to be movable with respect to the stator and rotor members. Thus, it is this latter relationship, instead of the concentricity of the stator to the rotor, which will vary to give alignment of the upper Ti the rotor 22 and the bearings 37 is wholly determined by the adjustment of screw means 55, as heretofore described. There is no need to provide shims or other spacer means for properly limiting the axial movement or end play of the rotor and shaft assembly during rotation.

With the parts in the final assembled relation, the bonding means 65 is then caused to be cured by any suitable means, such as by the application of a controlled amount of heat provided by kiln 69 with its controlled heating means 70, as shown in FIG. 5. Of course, any curing means may be employed; for example, with an adequate amount of hardener in the bonding means, the curing might be done at room temperature in a predetermined length of time. Therefore, the kiln is shown by way of illustration only. To eifect the curing, the assembly fixture with the assembled, but yet unbonded motor still arranged thereon, is placed in an upright position onto a belt-type conveyer 71 which is driven by motor and pulley means 72. The conveyer transports the motor and fixture assembly through the kiln at a regulated rate.

Since in the preferred method the shim means, holding the rotor and stator members concentric relative to each other, are of the meltable variety, it is essential that any application of heat must be applied in such a manner that setting or hardening of the bonding means is effected before the shim material melts, but it is not necessary that the bonding means be entirely cured, so long as the bonding means is hardened to a point wherein it will retain the rotor supporting means in a fixed relationship to the stator. Once the bonding means has been cured, the end shield assemblies 32 and 33 are rigidly secured to the outer surface of the stator core 21. Since the bearings 37 were freely mounted over rotor shaft 27 so as to be in the proper aligned position and further, since the bonding means, when cured, does not shrink or place any stress whatsoever between the rotor supporting means and the stator member, the alignment of the bearings and rotor is not affected in any way by the securement of the end shield assemblies to the stator. By the same token, the shim means, which is still in place in the air gap formed between the rotor and stator members, maintains the members in an accurate concentric relation, and upon'the curing of the bonding means, the members are then permanently held in such position through the end shields and the bearings.

The final step to be performed is the removal of the shim means by any suitable means, thereby freeing the rotor for rotation relative to the stator. This, of course, can be accomplished by any number of ways. In the preferred embodiment, the meltable shim means are removed simply by the additional heat applied to the assembly as it continues to pass through the kiln 69 after the bonding material has been cured. Of course, the application of heat, whether direct or indirect, must be such that the temperature sensitive parts of the motor; e.g., insulating parts, are unaifected. FIG. 6 depicts the fixture assembly and motor after removal from the conveyer subsequent to the final shim melting step. The shim means, as shown, has been melted and deposited onto the inner surface of the bottom end shield assembly 32, adhering thereto upon the discontinuance of the heating application. As heretofore pointed out, although the meltable shim means described provides the optimum in ease of assembly, mechanical shim means may be used in which case it is merely necessary to remove themthrough suitable openings provided in the end shields (not shown) after structurally strong in itself and must have the ability to.

adhere to difierent kinds of materials. Further, it should have the characteristic of flowing onto a surface, wetting the surface and staying Where it is initially placed until it becomes permanently hardened. Moreover, once the structural bonding material has been hardened or cured, it should be stable, i.e., thermo-setting in nature, and must not change from the solid form upon a certain amount of reheating, such as may be experienced during operation of the machine under various conditions.

The following examples are given in order to illustrate more clearly how the invention, as described above, has been carried forth in actual practice.

Example 1 Induction motor parts having the following dimensions were used:

1.755 max.

Rotor outer diameter min.

L 1.778 max. tailor bore diameter W miIL 3.211" max. Stator outer diameter W min.

End shields inner di- 3.245 max.

ameter of the flange 3.235 min.

In order to effect suitable shimming of the rotor and stator during assembly, the inner surface or bore of the stator was coated with Warcosine wax, a mixture including bees wax and paraffin, by an extruding and wiping process. While supported on an assembly fixture of the type heretofore disclosed, the end shields and bearings were assembled with the remainder of the parts, and structural adhesive bonding material was injected into the space between the outer section or flange of the end shields and the adjacent stator surface. The bonding material used was composed of an epoxy resin known as EA-ZOO (Copolymers Inc.) having a polyamide hardener or curing agent. The assembled motor and the supporting fixture were then placed in an oven, which had been preheated over 155 centigrade. After being subject to the heat of the oven for approximately seven minutes, the temperature of the ad: hesive bonding material was raised from room temperature to approximately centigrade. At this point, the adhesive bonding material had set sufliciently to retain the end shields in a fixed relationship with the stator.

The application of heat was continued foran additional two to three minutes until the wax in the air gap reached its melting temperature of approximately 69 centigrade. Although the wax melts at a temperature somewhat below that at which the adhesive bonding material tends to harden and set up, the temperature of the adhesive is raised more rapidly than. the temperature of the wax due to the different locations in the motor and different thermal characteristics of the respective materials. When the wax melted out of contact with the stator and rotor members, the members were freely rotatable relative to each other.

Heating of the motor was continued until the adhesive material'reached a maximum temperature of 148 centigrade. After the motor had been subjected to heat in the oven for a total time of sixteen minutes, thereby substantially curing the, adhesive material, the motor and supporting fixture were removed from the oven and allowed to cool. It was found that this construction provided for an exceedingly economical assembly, while at the same time, the air gap between the stator and the rotor was easily maintained within such close tolerances that an air gap of .006 and .010" is completely practical. Moreover, it was found that the resin, which experienced exceedingly little shrinkage upon curing, eifectively eliminated all stresses, both for the end shield and for the stator, and the bearings and rotor shaft were accurately aligned.

Example 2 A motor similarin construction to that of Example 1 material. Upon examination of the resultant motor itwas found that the motor had the same excellent air gap control and bearing and shaft alignment of the motor of Example 1.

Example 3 A motor having a .005" and .008" air gap was provided with shim means composed of .0047 thick steel strips. The same assembly method as for Example 1 was followed, except that instead of the adhesive material of Example 1, the following material was provided: epoxy resinwith an amine hardening or curing agent, bondmas- Iter M643, rubber and asbestos. The resin was then cured by heating the material to 65 C. for /2 hour. At this point, the shims were removed to leave the rotor and stator freely rotatable relative to each other. As before, the motor was provided with excellent bearing and shaft alignment as well as a finely controlled air gap.

The foregoing examples illustrate the fact that in practice, the assembly operation is exceedingly easy to employ and produces a machine having .a finely precise air gap and superior bearing and shaft alignment without difficulty.

As shown by the above examples, epoxy resin having a polyamide hardener and epoxy resin with an amine curing agent are two usable adhesive materials having adhesive qualities and very little shrinkage upon curing. In addition, other adhesive bonding materials will readily occur to mind such as phenol formaldehyde condensate and a polyvinylacetol (EC- 1300), rubber type cement, and cellulose sters dissolved in suitable solvents. It is further to be understood that the invention is intended to cover any suitable adhesive material including a curable organic resin of the type having very little shrinkage.

The resins are generally not: provided in their pure form, but are preferably mixed with fillers, both for reasons of economy and in order to provide a pastelike consistency which is more readily controllable for application purposes than a pure liquid or a powder, the form of most pure resins. Among the many fillers which may beused, includes: Cab-O-Sil, mica, titanium oxide, Wollastanite, glass fibers, silica, alumina, abestos, barium sulfate, and calcium carbonate.

With respect to the meltable shim means, the example above is not inclusive as to the materials which can be used. For example, shellac-wax combinations,-polyamides such as nylon, alkyds, and movalaks may be .used. Other materials will readily come to the mind of those skilled in the art. r

Also, it may well be that, rather than melting in the narrow sense (that is, going from a solid to a liquid state) some suitable material will be discovered which goes from the solid to the gaseous state directly, i.e., which sublimes like napthalene. Therefore, in order to cover any obvious applicable type of material, the term meltable is intended to be taken in its broader sense.

It should be apparent to those skilled in the art that the present invention is not limited to the preferred as: sembly procedure set forth above, but our improved method may be varied without a departure from the true scope and spirit of the invention. For instance, if desired, one end shield assembly could be fixedly secured to the stator assembly; i.e., the adhesive bonding material betweenthe two assemblies hardened by suitable means, before the addition of the second end shield assembly to the unit thereafter, the second end shield assembly could be rigidly attached to the stator assembly in the same manner previously described, thus completing the securement of the rotor supporting means to the stator assembly. The assembled motor would have the same accurate bearing and shaft alignment and controlled air gap, as the motor assembled by the preferred method. In addition, it will occur to those skilled in the art that our improved construction and method of assembly are inherently versatile and adaptable for use with a variety 'of motor types. For example, the motor illustrated in FIG. 1 could be made totally enclosed and still embody the present invention merly by forming the outer surface 64 of stator core 21 with a round configuration. The end shield assemblies 32 and 33, which comprise the rotor supporting means would take a cup-shaped form, and structural bonding material 65, as in FIG. 1, may be provided between the outer surface of the stator core and the adjacent portion of the end shield, thus enclosing the ends of the stator core and securing the end shield assemblies to the stator.

FIG. 8 illustrates another embodiment of our new and improved machine comprising an induction motor 74 having its end shield or end frame assemblies rigidly attached to opposite stator faces. The motor 74 may be assemblied by our improved method as described above with a minor adjustment of the fixture The assembled motor comprises a rotor 75 which is secured to a shaft 76 and is concentrically arranged within a stator 77, defining an air gap 78 therewith. The rotor member is similar in structure to the rotor of the embodiment "of FIG. 1; the stator is constructed of a plurality of laminations 79 of magnetic material, but its outer surface 80 is round, rather than generally rectangular like the stator illustrated in FIG. 1. Outwardly of the stator winding 81, the stator is provided with a plurality of apertures or holes 82 radially spaced at a predetermined distance from the longitudinal axis of the stator member. In the illustrated embodiment, these holes extend longitudinally through the stator, since this allows the use of a single type of punching, but it will be understood that recesses formed in the opposite stator faces could be used equally as well. r

Supported by the stator 77 and, in turn, supporting the rotor 75, are a pair of hell or cup shaped end shield assemblies 83 and 84. These end shield assemblies each contain a plurality of projections 85 which are adapted to be loosely received in holes 82. Bonding means 65 of the type described above is contained in holes 82, and rigidly secures the end shield assemblies to the stator. For supporting the rotor, each end shield assembly has fixedly secured thereto sintered bearings 86, adapted to carry the rotor and shaft assembly. As is in common practice today, each end shield assembly is further provided with a cylindrical oil impregnated felt body 87 for hearing and shaft lubricating purposes. Aperture 88 provides communication between the sintered bearing and the oil reserve. Thrust bearing means 89 and 90 are provided between each rotor end face 91 and 92 and the inner end of the bearings. It will be. seen that by the use of our improved 'method the rotor may be positioned concentrically within the stator and the bearings 86 are positively aligned on the shaft before the bonding material 65 is allowed to harden, thereby securing the end shields to the stator. Thus, here again, the desired positioning of the rotor supporting means is attained without any stressing of the parts and with the same ease of assembly as for the first embodi ment.

Referring now to FIG. 9, we have shown another em-. bodiment of the present invention assembled by our improved method of assembly outlined above. Illusa trated is an induction motor 93 of the totally. enclosed stator encapsulated type which is extremely moisture resistant. In the motor 93, stator 94 comprises a laminated magnetic core 95 having an accurately dimensioned radially inner surface 96 defining a rotor receiving annular bore. Coils 97, forming an exciting winding, are positioned on the core. A rotor member 98, which is secured to shaft 99, is concentrically positioned within the bore, forming air gap between the rotor 98 and stator surface 96. The stator 94 and coils 97 are enveloped in a solid impregnating compound 101, such as thermosetting impregnating varnish, whereby there is formed a stationary assembly 102. As shown, the rotor support- 11 ing means also forms a closure means and comprises two substantially cup-shaped end closures 103 and-1114, each having a shaft-receiving sintered bearing 105 rigidly mounted axially therethrough. As described for the modification illustrated by FIG. 8, bearing lubrication means. 106 are provided in each end shield; a thrust member 167 is secured to the shaft 59 at each end of the rotor between the rotor end ring 103 and the adjacent bearing 1115. The outer longitudinally extending pe riphery or annular side wall 1G9 of each end closure is adjacent to and preferably spaced from a portion 11a of the encapsulating material covering the coils. Structural adhesive bonding material 65 of the type described previously, fills the void between each closure member and the adjacent encapsulating material, thereby rigidly securing the rotor supporting means to the stationary assembly 102 and completing the enclosure of the rotor within the stationary assembly.

Therefore, like the machine embodiments shown in FIGS. 1 and 8, the improved totally encapsulated stator type motor illustrated by FIG. 9 has a rotor supporting means, including shaft bearings, attached to the stationary assembly solely by meansof the non-shrinking hardenrable structural adhesive bonding material. Thus, the totally encapsulated stator type motor is provided with an accurate alignment of the bearings and shaft as well as a closely controlled air gap between the rotor and stator members.

Yet another embodiment of the invention is illustrated in FIG. 10, which shows an assembled motor 111 of a type having detachable end shields, assembled in accordance with our improved manfacturing procedures. The stator and rotor members are laminated and similar in construction to those heretofore discussed, the rotor 112 being provided with a cast squirrel-cage winding 113 and the stator 114 being provided with coils 115 forming an exciting winding. A housing 116, formed of two substantially cylindrical cast iron members 117 and 118 respectively, surrounds the stator 114. The housing members 117 and 118 are secured together in any suitable fashion, such as by a rabbet joint 11?, and the stator 114 is rigidly bonded to the housing members, as indicated at 120. The ends 121 and 122 of the housing are closed by detachable end shields or platesv 123 and 124, which are secured thereto by screw means 125. These end shields, together with the housing members and the stator, form the complete stationary assembly 126.

Each end shield includes a centrally disposed aperture or opening 127 in which is mounted a rotor supporting means generally indicated at 128. The means 128 includes a flanged, cup-shaped element 129 which extends axially through, but is preferably radially spaced from the wall 131) of opening 127. Bearing 131 is fixedly mounted with the element 129 and carries one end of rotor shaft 132. Thrust bearing means 133 is fixedly positioned on the shaft between each bearing element 129 and the adjacent end face 134 of the rotor. Structural adhesive bonding material 65 of the type hereinbefore described fills the space between element 129 and the wall 130 of opening 127. This structural bonding material so holds the cup-shaped elements 129, that the bearings 131 are axially aligned, and the rotor and stator members are concentrically supported with a controlled air gap 135 therebetween.

Referm'ng now to FIG. 11, the present invention is shown as being incorporated in a unit bearing type motor 136. This motor, assembled according to the improved method previously discussed, is provided with a stator assembly 137 and a rotor assembly 138, concentrically arranged with an accurate air gap 135 therebetween. The stator 137 includes a laminated mag netic core member 140 with exciting windings 141; the rotor assembly 138 includes a generally cup-shaped rotor 142 and a shaft 143. As illustrated, the rotor has a laminated core 144 of magnetic material formed with winding slots 145 in which conductors 146 of a cast or fabricated squirrel cage winding. are arranged. A short circuiting end ring 147 is formed on one side of the laminated core 144. Another short circuiting end ring 148 is electrically connected to the other end of conductors 146 and extends over the side of, the laminated core 144, thereby providing an arrangement for retaining the laminations of the core 144 in an assembled relation between the end rings 147 and 148, and the winding conductors 146. The rotor is adapted to be mounted on the supporting shaft 143 by the provision of a hub portion 149 cast integral with the end ring 148 and secured to a sleeve 150 which is arranged in driving engagement with a splined or knurled end portion 151 of the shaft 143.

The stator assembly mounts a casting or frame 152, which serves as the rotor supporting means. As shown, the frame 152, formed of cast iron or die cast aluminum, extends as an end shield 153 at one end of the machine. The frame is provided with an outwardly extending web portion 154 formed integral with the end shield portion 153 and which has a central located hub 155 having a central bore 156. Shaft 143 is adapted tobe mounted for rotation in the centrally located hub 155. Shaft 143 is formed with a relieved section 157 of smaller diameter than the adjacent portions 158 and 159. The shaft portions 153 and 159 are rotatably supported by the cylindrical stationary bearing surfaces 166 and 1:61 of the central bore 155, whereby the shaft is journaled at spaced apart points. It will be noted that with this construction the rotor assembly is rotatably supported only by these hearings, both of which are on the same side of it, and there is no other support on the other side of the rotor. This arrangement is commonly referred to as a unit bearing motor. 7

A thrust washer 162, designed for carrying the weight of the rotor in one direction, is arranged on shaft 143 at the inner end of bearing 161, while a second thrust washer 163 for limiting movement of the rotor in the other direction is fixedly positioned on the shaft portion 164. A felt washer 163 is arranged between the thrust. washer 162 and the end of the sleeve 150 to cushion end bump and minimize resultant noise.

In order to provide suitable lubrication to the bearing surfaces of the shaft 143, a lubricant reservoir 1165 consisting of lubricant absorbing material, such as wool, may be provided in end shield cover 166. A lubricating feed- .lng wick 167, also of lubricant absorbing material, is

arranged into contact with shaft portion 168. Lubricant, such as any suitable oil, is placed in the reservoir and is substantially absorbed by the loose wool and the wick 167 such that it is fed at a desired rate to the shaft portion 168, from which it is fed along the bearing by a spiral groove 169 formed in the shaft portion 166 and passes into the pocket formed around the relieved portion 157 of the shaft and is then fed to the bear-ing engaging portion 161. The oil istheh thrown outwardly by oil slinger portion 1'70 formed on the inner end of sleeve 150 and is caught by an absorbent wick 171. An enclosing housing 172 is held concentric with the shaft bore by any suitable means, such as is generally indicated at 173 and is arranged to extend around the oil slinger 170 and wick 171 to provide an oil collection chamber. This housing 172 is arranged in communication with an oil return wick 174 which returns the lubricant from the collecting chamber to the oil reservoir 155. This type of lubricating system is described and claimed in the H. C. Bradley Patent No. 2,522,985 assignedto the same assignee of the present invention.

Frame 152 with its integrally formed bearing means is rigidly fastened to stator 137 by the same type structural adhesive bonding material 65 heretofore disclosed. The frame152 has an outer section with an integrally formed l3 flanged portion 175 immediately adjacent to and preferably spaced from the outer surface 176 of stator core 120. The structural adhesive bonding material 65 is provided between flange portion 175 and outer core surface 1'76. A second end shield cover 177 may be included to complete the enclosure of the stator and rotor assemblies.

With this construction, as is the case in all the machine embodiments heretofore described, an improved dynamoelectric machine has been provided in which the rotor supporting means, including the shaft bearings, is rigidly secured to the stationary assembly solely by means of the structural non-shrinking adhesive bonding material. Thus, the machine structure provides for accurate bearing alignment and excellent control of the air gap between the rotor and stator members.

It will be recognized from the foregoing disclosure that an important aspect of the improved method of assembly in the present invention is the maintenance of the rotor supporting means loosely adjustable relative to the stationary assembly with a hardenable non-shrinking structural bonding material therebetween, until the assembly of parts is complete, While at the same time, the rotor and stator members are being positively held in a predetermined spaced relation with respect to each other until the bonding material has been sufiiciently hardened to secure the rotor supporting means to the stationary assembly.

In practicing our present invention, it will occur to those skilled in the art that improved dynamoelectric machines may take other forms than those illustrated, when assembled by our improved method, without departing from the true spirit and scope of the invention. For example, axial air gap or pan cake machines; i.e., machines Which have the same electrical characteristics as the preferred machine embodiments illustrated herein, but mechanically differ in that the rotor turns in a plane parallel to rather than radially within the stator member, may be constructed with the rotor supporting means rigidly secured to the stationary assembly solely by means of the previously mentioned structural non-shrinking adhesive bonding material. The machine would have the same excellent air gap control and bearing alignment as described heretofore.

Of course, the present invention is equally adaptable to machines which have a controlled eccentricity of the air gap between the rotor and stator members. kind of machine could be assembled in accordance with the improved assembly procedure outlined above; however, the form of the shim means used would include shim means of different and controlled sizes positioned in the air gap between the rotor and stator members at predetermined locations, thereby building into the machine a controlled amount of air gap eccentricity.

It will be readily manifest from the foregoing that the advantages of this invention are numerous. The machine construction provides for an accurate alignment of the bearings and shaft, and for a close control of the air gap between the rotor and stator members. Moreover, the improved method of assembly of the invention permits a mass production manufacture of a uniformly high quality machine having excellent operating characteristics, with a minimum amount of variance between machines and at a unit cost considerably lower than has been accomplished heretofore. More specifically, the number and cost of the individual manufacturing operations have This lid

been reduced while the accuracy thereof has been improved. Further, machines are produced devoid of stresses which would tend to deform the alignment of either the bearings and the shaft or the rotor and stator. In addition, inexpensive parts may be used without affooting the accurate alignment of the various components. Moreover, the desired amount of rotor and shaft end play is easily set into the machine. Finally, due to the simplicity of the improved assembly method, it is suitable for use with a variety of machine types.

While the present invention has been described by reference to particular embodiments thereof, it is to be understood that numerous modifications may be made by those skilled in the art without actually departing from the invention. We therefore aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A permanently assembled dynamoelectric machine comprising a stationary member including a magnetic stator core having an outer surface and an inner surface defining a bore, and two end surfaces with at least one of said end surfaces having a plurality of holes formed therein spaced radially between and spaced from said inner and outer surfaces, a shaft, a rotatable'member secured to said shaft and concentrically positioned within said bore and spaced from said inner surface of said stationary member, at least one end frame assembly supporting said rotatable member, one end frame assembly being positioned adjacent the end surface of said stationary member having holes, a shaft-carrying bearing fixedly mounted in said end frame assembly in axial alignment with said bore, said one end shield assemblies having portions projecting into at least some of said holes in spaced relation to said stator core, and structural adhesive bonding material disposed within the holes accommodating said end frame portions rigidly bonding said one end frame assembly to said stationary member in a permanently fixed relation for the operating life of the machine.

2. The dynamoelectric machine of claim 1 in which the magnetic stator core is formed of a stack of laminations each having axially aligned openings to define said plurality of holes entirely through said core, an end frame assembly arranged adjacent each end surface of said stator core, each of said end frame assemblies including portions projecting axially into the same holes in spaced relation to said stator core, and thermoresponsive structural adhesive bonding material disposed within said holes securing said end frame assemblies and stator core rigidly together.

References Cited by the Examiner UNITED STATES PATENTS 2,531,334 11/50 Grenat 30872 X 2,542,043 2/51 Nagel -a 154-43 2,643,351 6/53 Fiertag 310-258 2,650,992 9/53 Forss et al. 310-42 2,763,052 9/56 Elmer 29-155.5 2,804,680 9/57 Flagg 29-1555 2,814,744 11/57 Demetriou et al 3l0-43 2,922,902 1/60 Hargreaves 3l0-43 2,953,699 9/60 Redding 3l0258 MILTON O. HIRSHFIELD, Primary Examiner. 

1. A PERMANENTLY ASSEMBLED DYNAMOELECTRIC MACHINE COMPRISING A STATIONARY MEMBER INCLUDING A MAGNETIC STATOR CORE HAVING AN OUTER SURFACE AND AN INNER SURFACE DEFINING A BORE, AND TWO END SURFACES WITH AT LEAST ONE OF SAID END SURFACES HAVING A PLURALITY OF HOLES FORMED THEREIN SPACED RADIALLY BETWEEN AND SPACED FROM SAID INNER AND OUTER SURFACES, A SHAFT, A ROTATABLE MEMBER SECURED TO SAID SHAFT AND CONCENTRICALLY POSITIONED WITHIN SAID BORE AND SPACED FROM SAID INNER SURFACE OF SAID STATIONARY MEMBER, AT LEAST ONE END OF FRAME ASSEMBLY SUPPORTING SAID ROTATABLE MEMBER, ONE END FRAME ASSEMBLY BEING POSITIONED ADJACENT THE END SURFACE OF SAID STATIONARY MEMBER HAVING HOLES, A SHAFT-CARRYING BEARING FIXEDLY MOUNTED IN SAID END FRAME ASSEMBLY IN AXIAL ALIGNMENT WITH SAID BORE, SAID ONE END SHIELD ASSEMBLIES HAVING PORTIONS PROJECTING INTO AT LEAST SOME OF SAID HOLES IN SPACED RELATION TO SAID STATOR CORE, AND STRUCTURAL ADHESIVE BONDING MATERIAL DISPOSED WITHIN THE HOLES ACCOMMODATING SAID END FRAME PORTIONS RIGIDLY BONDING SAID ONE END FRAME ASSEMBLY TO SAID STATIONARY MEMBER IN A PERMANENTLY FIXED RELATION FOR THE OPERATING LIFE OF THE MACHINE. 